示例
这是一个演示SQLite数据库用法的示例。它创建了一个基本的联系人应用程序，该应用程序允许插入，删除和修改联系人。要尝试使用此示例，您需要在支持相机的实际设备上运行它。
- 您将使用Android Studio创建一个Android应用程序，并将其命名为Demo，位于com.jc2182.demo包下，如Hello World示例一章中所述。
- 修改src/MainActivity.java文件以获取所有XML组件的引用，并在listView上填充联系人。
- 创建新的src/DBHelper.java来管理数据库工作
- 创建一个新的Activity作为DisplayContact.java，它将在屏幕上显示该联系人
- 修改res/layout/activity_main以添加相应的XML组件
- 修改res/layout/activity_display_contact.xml以添加相应的XML组件
- 修改res/values/string.xml以添加必要的字符串组件
- 修改res/menu/display_contact.xml以添加必要的菜单组件
- 创建一个新菜单为res/menu/mainmenu.xml以添加插入联系人选项
- 运行该应用程序以启动Android模拟器并验证在该应用程序中所做更改的结果。
以下是修改后的主要活动文件src/com.jc2182.demo/MainActivity.java的内容。
package com.jc2182.demo;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.ArrayList;
public class MainActivity extends Activity {
public final static String EXTRA_MESSAGE = "MESSAGE";
private ListView obj;
DBHelper mydb;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mydb = new DBHelper(this);
ArrayList array_list = mydb.getAllCotacts();
ArrayAdapter arrayAdapter=new ArrayAdapter(this,android.R.layout.simple_list_item_1, array_list);
obj = (ListView)findViewById(R.id.listView1);
obj.setAdapter(arrayAdapter);
obj.setOnItemClickListener(new AdapterView.OnItemClickListener(){
@Override
public void onItemClick(AdapterView arg0, View arg1, int arg2,long arg3) {
// TODO Auto-generated method stub
int id_To_Search = arg2 + 1;
Bundle dataBundle = new Bundle();
dataBundle.putInt("id", id_To_Search);
Intent intent = new Intent(getApplicationContext(),DisplayContact.class);
intent.putExtras(dataBundle);
startActivity(intent);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main_menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item){
super.onOptionsItemSelected(item);
switch(item.getItemId()) {
case R.id.item1:Bundle dataBundle = new Bundle();
dataBundle.putInt("id", 0);
Intent intent = new Intent(getApplicationContext(),DisplayContact.class);
intent.putExtras(dataBundle);
startActivity(intent);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public boolean onKeyDown(int keycode, KeyEvent event) {
if (keycode == KeyEvent.KEYCODE_BACK) {
moveTaskToBack(true);
}
return super.onKeyDown(keycode, event);
}
}
以下是修改后的主要活动文件src/com.jc2182.demo/DBHelper.java的内容。
package com.jc2182.demo;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.util.ArrayList;
import java.util.HashMap;
public class DBHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "MyDBName.db";
public static final String CONTACTS_TABLE_NAME = "contacts";
public static final String CONTACTS_COLUMN_NAME = "name";
public static final String CONTACTS_COLUMN_EMAIL = "email";
public static final String CONTACTS_COLUMN_STREET = "street";
public static final String CONTACTS_COLUMN_CITY = "place";
public static final String CONTACTS_COLUMN_PHONE = "phone";
private HashMap hp;
public DBHelper(Context context) {
super(context, DATABASE_NAME , null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL( "create table contacts " + "(id integer primary key, name text,phone text,email text, street text,place text)"
);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS contacts");
onCreate(db);
}
public boolean insertContact (String name, String phone, String email, String street,String place) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("name", name);
contentValues.put("phone", phone);
contentValues.put("email", email);
contentValues.put("street", street);
contentValues.put("place", place);
db.insert("contacts", null, contentValues);
return true;
}
public Cursor getData(int id) {
SQLiteDatabase db = this.getReadableDatabase();
Cursor res = db.rawQuery( "select * from contacts where id="+id+"", null );
return res;
}
public int numberOfRows(){
SQLiteDatabase db = this.getReadableDatabase();
int numRows = (int) DatabaseUtils.queryNumEntries(db, CONTACTS_TABLE_NAME);
return numRows;
}
public boolean updateContact (Integer id, String name, String phone, String email, String street,String place) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues contentValues = new ContentValues();
contentValues.put("name", name);
contentValues.put("phone", phone);
contentValues.put("email", email);
contentValues.put("street", street);
contentValues.put("place", place);
db.update("contacts", contentValues, "id = ? ", new String[] { Integer.toString(id) } );
return true;
}
public void deleteContact (Integer id) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete("contacts",
"id = ? ",
new String[]{Integer.toString(id)});
}
public ArrayList<String> getAllCotacts() {
ArrayList<String> array_list = new ArrayList<String>();
//hp = new HashMap();
SQLiteDatabase db = this.getReadableDatabase();
Cursor res = db.rawQuery( "select * from contacts", null );
res.moveToFirst();
while(res.isAfterLast() == false){
array_list.add(res.getString(res.getColumnIndex(CONTACTS_COLUMN_NAME)));
res.moveToNext();
}
return array_list;
}
}
以下是修改后的主要活动文件src/com.jc2182.demo/DisplayContact.java的内容。
package com.jc2182.demo;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class DisplayContact extends Activity {
private DBHelper mydb;
TextView name;
TextView phone;
TextView email;
TextView street;
TextView place;
int id_To_Update = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_display_contact);
name = (TextView) findViewById(R.id.editTextName);
phone = (TextView) findViewById(R.id.editTextPhone);
email = (TextView) findViewById(R.id.editTextStreet);
street = (TextView) findViewById(R.id.editTextEmail);
place = (TextView) findViewById(R.id.editTextCity);
mydb = new DBHelper(this);
Bundle extras = getIntent().getExtras();
if (extras != null) {
int Value = extras.getInt("id");
if (Value > 0) {
//means this is the view part not the add contact part.
Cursor rs = mydb.getData(Value);
id_To_Update = Value;
rs.moveToFirst();
String nam = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_NAME));
String phon = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_PHONE));
String emai = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_EMAIL));
String stree = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_STREET));
String plac = rs.getString(rs.getColumnIndex(DBHelper.CONTACTS_COLUMN_CITY));
if (!rs.isClosed()) {
rs.close();
}
Button b = (Button) findViewById(R.id.button1);
b.setVisibility(View.INVISIBLE);
name.setText((CharSequence) nam);
name.setFocusable(false);
name.setClickable(false);
phone.setText((CharSequence) phon);
phone.setFocusable(false);
phone.setClickable(false);
email.setText((CharSequence) emai);
email.setFocusable(false);
email.setClickable(false);
street.setText((CharSequence) stree);
street.setFocusable(false);
street.setClickable(false);
place.setText((CharSequence) plac);
place.setFocusable(false);
place.setClickable(false);
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
Bundle extras = getIntent().getExtras();
if (extras != null) {
int Value = extras.getInt("id");
if (Value > 0) {
getMenuInflater().inflate(R.menu.display_contact, menu);
} else {
getMenuInflater().inflate(R.menu.main_menu,menu);
}
}
return true;
}
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);
switch (item.getItemId()) {
case R.id.Edit_Contact:
Button b = (Button) findViewById(R.id.button1);
b.setVisibility(View.VISIBLE);
name.setEnabled(true);
name.setFocusableInTouchMode(true);
name.setClickable(true);
phone.setEnabled(true);
phone.setFocusableInTouchMode(true);
phone.setClickable(true);
email.setEnabled(true);
email.setFocusableInTouchMode(true);
email.setClickable(true);
street.setEnabled(true);
street.setFocusableInTouchMode(true);
street.setClickable(true);
place.setEnabled(true);
place.setFocusableInTouchMode(true);
place.setClickable(true);
return true;
case R.id.Delete_Contact:
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage(R.string.deleteContact)
.setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
mydb.deleteContact(id_To_Update);
Toast.makeText(getApplicationContext(), "Deleted Successfully", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(getApplicationContext(), MainActivity.class);
startActivity(intent);
}
}).setNegativeButton(R.string.no, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
// User cancelled the dialog
}
});
AlertDialog d = builder.create();
d.setTitle("Are you sure");
d.show();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public void run(View view) {
Bundle extras = getIntent().getExtras();
if (extras != null) {
int Value = extras.getInt("id");
if (Value > 0) {
if (mydb.updateContact(id_To_Update, name.getText().toString(),
phone.getText().toString(), email.getText().toString(),
street.getText().toString(), place.getText().toString())) {
Toast.makeText(getApplicationContext(), "Updated", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(getApplicationContext(), MainActivity.class);
startActivity(intent);
} else {
Toast.makeText(getApplicationContext(), "not Updated", Toast.LENGTH_SHORT).show();
}
} else {
if (mydb.insertContact(
name.getText().toString(),
phone.getText().toString(),
email.getText().toString(),
street.getText().toString(),
place.getText().toString())) {
Toast.makeText(
getApplicationContext(),
"done",
Toast.LENGTH_SHORT)
.show();
} else {
Toast.makeText(
getApplicationContext(),
"not done",
Toast.LENGTH_SHORT)
.show();
}
Intent intent = new Intent(getApplicationContext(), MainActivity.class);
startActivity(intent);
}
}
}
}
以下是res/layout/activity_main.xml文件的内容-
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/textView"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:textSize="30dp"
android:text="数据库操作示例" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="菜鸟教程"
android:id="@+id/textView2"
android:layout_below="@+id/textView"
android:layout_centerHorizontal="true"
android:textSize="35dp"
android:textColor="#ff16ff01" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/imageView"
android:layout_below="@+id/textView2"
android:layout_centerHorizontal="true"
android:background="#112233ee"
android:src="@drawable/logo"/>
<ScrollView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/scrollView"
android:layout_below="@+id/imageView"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true">
<ListView
android:id="@+id/listView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true" >
</ListView>
</ScrollView>
</RelativeLayout>
以下是res/layout/activity_display_contact.xml文件的内容-
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/scrollView1"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".DisplayContact" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="00dp">
<EditText
android:id="@+id/editTextName"
android:layout_width="280dp"
android:layout_height="wrap_content"
android:layout_marginTop="5dp"
android:layout_toEndOf="@+id/textView1"
android:ems="10"
android:inputType="text" />
<TextView
android:id="@+id/textView1"
android:layout_width="83dp"
android:layout_height="49dp"
android:text="@string/name"
android:textAppearance="?android:attr/textAppearanceMedium" />
<TextView
android:id="@+id/textView5"
android:layout_width="83dp"
android:layout_height="49dp"
android:layout_below="@+id/textView1"
android:text="@string/phone"
android:textAppearance="?android:attr/textAppearanceMedium" />
<EditText
android:id="@+id/editTextPhone"
android:layout_width="274dp"
android:layout_height="wrap_content"
android:layout_below="@+id/editTextName"
android:layout_toEndOf="@+id/textView5"
android:layout_marginTop="10dp"
android:ems="10"
android:inputType="phone|text" />
<TextView
android:id="@+id/textView4"
android:layout_width="83dp"
android:layout_height="49dp"
android:layout_below="@+id/textView5"
android:text="@string/street"
android:textAppearance="?android:attr/textAppearanceMedium" />
<EditText
android:id="@+id/editTextStreet"
android:layout_width="278dp"
android:layout_height="wrap_content"
android:layout_below="@id/editTextPhone"
android:layout_toEndOf="@+id/textView4"
android:layout_marginTop="9dp"
android:ems="10"
android:inputType="text" />
<TextView
android:id="@+id/textView2"
android:layout_width="76dp"
android:layout_height="41dp"
android:layout_alignLeft="@+id/textView1"
android:layout_alignBottom="@+id/editTextEmail"
android:text="@string/email"
android:textAppearance="?android:attr/textAppearanceMedium" />
<EditText
android:id="@+id/editTextEmail"
android:layout_width="276dp"
android:layout_height="wrap_content"
android:layout_below="@+id/editTextStreet"
android:layout_alignStart="@+id/editTextStreet"
android:layout_marginTop="9dp"
android:ems="10"
android:inputType="textEmailAddress" />
<TextView
android:id="@+id/textView3"
android:layout_width="104dp"
android:layout_height="26dp"
android:layout_alignBaseline="@+id/editTextCity"
android:layout_alignParentLeft="true"
android:layout_marginLeft="0dp"
android:layout_toLeftOf="@+id/editTextEmail"
android:text="@string/country"
android:textAppearance="?android:attr/textAppearanceMedium" />
<EditText
android:id="@+id/editTextCity"
android:layout_width="274dp"
android:layout_height="wrap_content"
android:layout_below="@+id/editTextEmail"
android:layout_alignEnd="@+id/editTextName"
android:layout_marginTop="30dp"
android:ems="10"
android:inputType="text" />
<Button
android:id="@+id/button1"
android:layout_width="104dp"
android:layout_height="62dp"
android:layout_alignStart="@+id/editTextCity"
android:layout_alignParentBottom="true"
android:layout_below="@+id/editTextCity"
android:layout_marginLeft="-5dp"
android:layout_marginBottom="2dp"
android:onClick="run"
android:text="@string/save" />
</RelativeLayout>
</ScrollView>
以下是res/value/string.xml的内容
<resources>
<string name="app_name">Demo</string>
<string name="Add_New">添加新的</string>
<string name="edit">编辑联系人</string>
<string name="delete">删除联系人</string>
<string name="title_activity_display_contact">显示联系人</string>
<string name="name">姓名</string>
<string name="phone">电话</string>
<string name="email">邮箱</string>
<string name="street">街道</string>
<string name="country">城市/省份/国家</string>
<string name="save">保存联系人</string>
<string name="deleteContact">您确定要删除他/她？</string>
<string name="yes">是</string>
<string name="no">否</string>
</resources>
以下是res/menu/main_menu.xml的内容
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android" >
<item android:id="@+id/item1"
android:icon="@drawable/ic_launcher"
android:title="@string/Add_New" >
</item>
</menu>
以下是AndroidManifest.xml的内容
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.jc2182.demo"
android:installLocation="auto">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:usesCleartextTraffic="true"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".DisplayContact"/>
</application>
</manifest>
让我们尝试运行刚刚修改的应用程序。我假设您在进行环境设置时已创建了AVD。要从Android Studio运行该应用，请打开您项目的活动文件之一，然后工具栏中单击“运行”图标。Android studio将应用程序安装在您的AVD上并启动它，如果设置和应用程序一切正常，它将显示在“模拟器”窗口下面-
按munu键出现
点击联系人，返回到第一张页面
按munu键出现
点击联系人，返回到第一张页面
